Ns-2 Tutorial (1) Multimedia Networking Group, The Department of Computer Science, UVA Jianping Wang Jianping Wang, 2002 cs757 1.

ns-2 Tutorial (1)

Multimedia Networking Group,

The Department of Computer Science, UVA

Jianping Wang

Jianping Wang, 2002 cs757 1

Contents:

• Objectives of this week

• What is ns-2?

• Working with ns-2

• Tutorial exercise

• ns-2 internals

• Extending the C++ part of ns-2

• Hands-on: Wireless

• Other ns-2 related software

Jianping Wang, 2002 cs757 2

Today

Partly adopted from Nicolas’ slides.

Objectives of this week

• Get some exposure to one of the most useful tools in networking research and development.

• Understand and work with a popular network simulator.

• Get a better understanding of the networking dynamics.

• “Smooth the learning curve”.

Jianping Wang, 2002 cs757 3

What is ns-2?

• ns-2 stands for Newwork Simulator version 2.• ns-2:

• Is a discrete event simulator for networking research

• Work at packet level.

• Provide substantial support to simulate bunch of protocols like TCP, UDP, FTP, HTTP and DSR.

• Simulate wired and wireless network.

• Is primarily Unix based.

• Use TCL as its scripting language.

• ns-2 is a standard in research community.

Jianping Wang, 2002 cs757 4

tcl8.0

otcl

tclcl

UIEventScheduler

Netw

orkC

omponent

What is ns-2 (cont.) ?

• otcl: Object-oriented support• tclcl: C++ and otcl linkage• Discrete event scheduler• Data network (the Internet) components

Jianping Wang, 2002 cs757 5

C++

Other Network Simulators

• OPNET (http://www.opnet.com)• Commercial Software

• Support Windows and Unix

• Graphical Interface

• Not free

• GloMoSim (http://pcl.cs.ucla.edu/projects/glomosim)• Simulation enviroment for wireless network

• Scalable to support thousands of nodes

• Using layered approach to build different simulation layers

• Free for educational usersJianping Wang, 2002 cs757 6

Working with ns-2

Jianping Wang, 2002 cs757 7

Getting Started: Install ns-2

• Download software package from:

http://www.isi.edu/nsnam/ns/

- Easy installation way: all at once• The latest version is 2.1b9a released at July 3, 2002.

It contains:- Tk release 8.3.2

- Otcl release 1.0a8

- TclCL release 1.0b12

- Tcl release 8.3.2

- Ns release 2.1b9a

- Nam release 1.0a11a

- Xgraph version 12

- CWeb version 3.4g

- SGB version 1.0

- Gt-itm gt-itm and sgb2ns 1.1

- Zlib version 1.1.3

Jianping Wang, 2002 cs757 8

Running ns-2 program

ns-2 Program(Otcl Script)

$ns ns-2_file

. Otcl expretenter

. NS simulator libries

SimulationResults

(trace files)

AnalysisRun ns-2Program

. Read trace file

. Replay with nam

. Draw statistical pictures

Jianping Wang, 2002 cs757 9

Hello World - Interactive Mode

[jwang@iodine jwang]$ ns

% set ns [new Simulator]

_o4

% $ns at 1 “puts \“Hello World!\””

1

% $ns at 1.5 “exit”

2

% $ns run

Hello World!

[jwang@iodine jwang]$Jianping Wang, 2002 cs757 10

Hello World - Batch Mode

simple.tcl:set ns [new Simulator]

$ns at 1 “puts \“Hello World!\””

$ns at 1.5 “exit”

$ns run

[jwang@iodine jwang]$ ns simple.tcl

Hello World![jwang@iodine jwang]$

Jianping Wang, 2002 cs757 11

Basic tclproc test {} {

set a 43 ; a = 43

set b 27 ; b = 27

set c [expr $a + $b] ; c = a + b

set d [expr [expr $a - $b] * $c] ; d = (a – b) * c

for {set k 0} {$k < 10} {incr k} { ; for (k=0; k<10; k++)

puts “k = $k”

}

}

Jianping Wang, 2002 cs757 12

Basic otclClass mom

mom instproc greet {} {

$self instvar age_

puts “$age_ years old mom: How are you doing?”

}

Class kid -superclass mom

kid instproc greet {} {

$self instvar age_

puts “$age_ years old kid: What’s up, dude?”

}

set a [new mom]

$a set age_ 45

set b [new kid]

$b set age_ 15

$a greet

$b greet

Jianping Wang, 2002 cs757 13

Basic ns-2

• Create a new simulator object• [Turn on tracing]

– [Open your own trace files]

• Create network (physical layer)• Create link and queue (data-link layer)• Define routing protocol• Create transport connection (transport layer)• Create traffic (application layer)• Insert errors

Jianping Wang, 2002 cs757 14

Creating Simulator Instance

• Create simulator instanceset ns [new Simulator]- Usually the first non-comment statement in ns-

2 script- Initialize the packet format- Create a scheduler (default is a calendar

scheduler)- Create a “null agent”

Jianping Wang, 2002 cs757 15

Turning on a Tracefile

• Open file for NS tracing

set f [open out.tr w]

$ns trace-all $f

• Open file for nam tracing set nf [open out.nam w]

$ns namtrace-all $nf

• Open your own trace fileset my_f [open my_out.tr w]

puts $my_f “[$ns now] [expr $x(1) + $y(1)]”Jianping Wang, 2002 cs757 16

Creating a Network(1)

Jianping Wang, 2002 cs757 17

h1

h2

r1 r2

h3

h4

10Mb, 2ms

10Mb, 4ms10Mb, 2ms

10Mb, 3ms

1.5Mb, 20ms

host

router router

host

hosthost

• Network topology

Creating a Network (2)

• Creating nodes

set node_(h1) [$ns node]

set node_(h2) [$ns node]

set node_(r1) [$ns node]

set node_(r2) [$ns node]

set node_(h3) [$ns node]

set node_(h4) [$ns node]

Jianping Wang, 2002 cs757 18

Creating a Network(3)

• Creating Link and Queue$ns duplex-link $node_(h1) $node_(r1) 10Mb 2ms DropTail

$ns duplex-link $node_(h2) $node_(r2) 10Mb 3ms DropTail

$ns duplex-link $node_(r1) $node_(r2) 1.5Mb 20ms DropTail

$ns queue-limit $node_(r1) $node_(r2) 50

……

Jianping Wang, 2002 cs757 19

Creating a TCP connectionset tcp0 [$ns create-connection TCP/Reno $node_(s1)

TCPSink/DelAck $node_(s4) 0]

Jianping Wang, 2002 cs757 20

S1

S2

R1 R2

S2

S2

10Mb, 2ms

10Mb, 4ms

10Mb, 2ms

10Mb, 3ms

1.5Mb, 20ms

Creating traffic

• Attaching FTP traffic on the top of TCP set ftp0 [$tcp0 attach-app FTP]

Jianping Wang, 2002 cs757 21

S1

S2

R1 R2

S2

S2

10Mb, 2ms

10Mb, 4ms

10Mb, 2ms

10Mb, 3ms

1.5Mb, 20ms

FTP Server

FTP Client

Insert Errors

set loss_module [new ErrorModel]

$loss_module set rate_ 0.01

$loss_module unit pkt

$loss_module ranvar [new RandomVariable/Uniform]

$loss_module drop-target [new Agent/Null]

$ns lossmodel $loss_module $n0 $n1

Jianping Wang, 2002 cs757 22

Summary

Topology

Attach-agentAttach-agent

ProtocolStack

Application

Connection

Jianping Wang, 2002 cs757 23

Start/Stop ns• Schedule an event to start traffic at time 1.0

$ns at 1.0 "$ftp0 start“• Schedule an event to stop ns at time 17.0

$ns at 17.0 "$ftp0 stop“• Start ns

$ns run

- last statement• Stop ns

exit 0Jianping Wang, 2002 cs757 24

Visualization Tool: nam

• Replay events from a nam trace file

• The nam trace file can be huge when simulation time is long or events happen intensively. Be careful!

• Run nam:– $nam nam_trace_file.nam– In ns-2 script:

Proc finish{} {

……

exec nam nam_trace_file.nam &

exit

}Jianping Wang, 2002 cs757 25

Jianping Wang, 2002 cs757 26

Draw Plots Using Xgraph

• Create your own output files

• Collect statistical data synchronized.

• Run xgraph:– $xgraph out0.tr, out1.tr –geometry 800x400– In ns-2 script:

Proc finish{} {

……

exec xgraph out0.tr, out1.tr –geometry 800x400 &

exit

}

Jianping Wang, 2002 cs757 27

Useful URLs

• http://www.isi.edu/nsnam/ns - the official ns homepage

• http://www.isi.edu/nsnam/ns/ns-documentation.html - ns manual

• http://jan.netcomp.monash.edu.au/ProgrammingUnix

/tcl/tcl_tut.html - Tcl tutorial

• http://bmrc.berkeley.edu/research/cmt/cmtdoc/otcl/ - oTcl tutorial

Jianping Wang, 2002 cs757 28